- Add a granule hopper that mounts on the top of LISA and feeds granules through a hole in the center of the top board

- Granules are held by a trap door that is mechanically opened by the extruder head parking against it

- Granules fill a magazine in the extruder head

- Extruder primes and continues

- Switch magazine out when you change color/to avoid bleed

- Multiple trap doors for different materials/colors/mixing?

- Magazine spring-extends automatically when empty, so it can catch the trapdoor again?

Maybe the magazines live in the trap door, and a heated basalt top is drilled out to contain them. At 50% of melt temperature? The magazine is taller than the top is thick, so the heat is directed to a strategic area.

Borosilicate glass chamber/pre-nozzle that downsizes through a small piece of high-temp silicone tubing and a nozzle? Plenty of borosilicate pipettes and pieces that are relatively affordable.

Do you run a screw or can you apply pressure? CO2 is cheap..

Apply a small current to a sleeve somewhere and we have a contact point for a calibration brush?

You are only heating and controlling a small amount of material.. but the devil is in making the details affordable.